Sheriff's officials said Monday a preliminary investigation determined the cause of death was suicide due to asphyxia. Williams was 63 and had suffered for years from periodic bouts of substance abuse and depression.

Williams' press representative Mara Buxbaum said the actor had been battling severe depression recently. Just last month, Williams announced he was returning to a 12-step treatment program.

Coroner's officials say he was last seen alive at home around 10 p.m. Sunday.